Download Soil, sand, pollen

Soil Analysis
“Life is hard. Then you die.
Then they throw dirt in your face.
Then the worms eat you.
Be grateful it happens in that order.”
—David Gerrold, American science fiction writer
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Soil Comparisons
 May establish a relationship or link to the
crime, the victim, or the suspect(s)
 Physical properties—density,
magnetism, particle size, mineralogy
 Chemical properties—pH, trace
elements
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Probative Value
of Soil
 Types of earth material are virtually
unlimited. They have a wide distribution
and change over short distances.
 As a result, the statistical probability of a
given sample having properties the same
as another is very small
 Evidential value of soil can be excellent
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Increasing
Probative Value
 Rare or unusual
minerals
 Rocks
 Fossils
 Manufactured
particles
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Minerals
 More than 2000 have been identified
 Twenty or so are commonly found in soils;
most soil samples contain only 3 to 5
 Characteristics for identification—size,
density, color, luster, fracture, streak, or
magnetism
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Rocks
 Aggregates of minerals
 Types
 Natural—like granite
 Man-made—like concrete
 Formation
 Igneous
 Sedimentary
 Metamorphic
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Fossils
 Remains of plants and animals
 May help geologists to determine the age
of rocks
 Some are scarce and can be used to
identify regions or locations
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Soil Evidence
 Class characteristics—the type of soil
may have similar characteristics at the
primary and/or secondary crime scene, on
the suspect or on the victim
 Individual characteristics—only if the
soil has an unusual or specialized
ingredient such as pollen, seeds,
vegetation, or fragments.
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Sand
 Sand is the term applied to natural particles
with a grain diameter between 1/16 mm
and 2 mm.
 Its color and contents are dependent upon
the parent rock and surrounding plant and
animal life.
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Sand Types
 Continental sands—formed from weathered
continental rock, usually granite
 Ocean floor sands—formed from volcanic
material, usually basalt
 Carbonate sands—composed of various forms
of calcium carbonate
 Tufa sands—formed when calcium ions from
underground springs precipitate with carbonate
ions in the salt water of a salt lake
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Sand Evidence
“In every grain of sand is a story of earth.”
—Rachel Carson
 Class characteristics—the type of sand may
have similar characteristics to the primary
and/or secondary crime scene, on the suspect
or on the victim
 Individual characteristics—only if the sand
has an unusual ingredient or contaminant.
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Palynology
 The study of pollen and spores
 Important to know:
 What is produced in a given area
 The dispersal pattern
 Variation in size and weight
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Pollen-Producing Plants
Forensic palynologists know each pollen-producing plant
provides a pollen fingerprint—a specific type of pollen
grain. They also know there will be a certain number of
grains found in a specific geographical area during
particular times of the year.
– Examples of non-seed plants would be ferns,
mosses, liverworts, and horsetails.
– Examples of seed plants would be gymnosperms
(cycads, ginkgoes, and conifers like an evergreen)
and angiosperms (flowering plants like roses).
Forensic Science:
Chapter
13
Fundamentals
&
Investigations, Chapter
12
Pollen and Spore Identification
in Solving Crimes
Angiosperm pollen grains
Gymnosperm pollen grains
• The outer shell of a pollen grain and spore has a complex
•
•
and unique structure.
These are revealed under a microscope.
Identification can provide important trace evidence in
solving crimes.
Forensic Science:
Chapter
13
Fundamentals
&
Investigations, Chapter
13
Forensic Geology
in the News
A 9-year-old’s body was found in a wooded
area along a river in Lincoln County, South
Dakota. A forensic geologist collected soil
samples from the fenders of a suspect’s truck
and the area where the body was found. Both
soils contained grains of a blue mineral that
turned out to be gahnite, a rare mineral that had
never been reported in South Dakota. As a result,
the soil tied the suspect to the crime.
Check out other cases at:
www.forensicgeology/science.htm
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